The train solution you found sounds reasonable to me. The connections between Strasbourg and Germany never were very good. There used to be slow international trains to Munich and further to Vienna and there are now some TGV but the high-speed rail network does not extend all the way to Strasbourg yet and the fastest trains to France run further north, from Frankfurt over Saarbrücken and Mannheim to Paris without stopping elsewhere in France.
The price also sounds about right for this distance in Germany, as train travel is relatively expensive there. Still, there are two ways to pay less than that:
- The Schönes Wochenende or Quer-durchs-Land tickets cost EUR 44 and allow you to travel all day but only on regional trains, which means even more stopovers and longer travel times.
- Since your final destination is outside Germany, the journey qualifies for an Europa-Spezial-Ticket, which means the cheapest fare is EUR 39. However, you have to be flexible and book long in advance to get it. On bahn.de, you can use the Sparpreis-Finder to look for them more easily than using the regular search function.
As for other transportation modes, flying is unlikely to be attractive but buses might be cheaper than the train. Rome2rio is very useful for these kinds of comparisons. You can also find more info on bus travel in Germany in previous questions:
Finally, another option is ride sharing, which is quite popular in Germany (you have to look for “Mitfahrgelegenheit”).